JP2025158084A - Resist composition and pattern forming method - Google Patents

Abstract

The present invention provides a non-chemically amplified resist composition that exhibits excellent sensitivity and resolution in photolithography using high-energy rays, and a pattern formation method that uses the resist composition.
The resist composition includes a hypervalent iodine compound represented by the following formula (1), a carboxy group-containing polymer, and a solvent.
[Selection diagram] None

Description

The present invention relates to a resist composition and a pattern formation method.

As the IoT market expands, there is a growing demand for higher integration, higher speeds, and lower power consumption in LSIs, leading to rapid progress in miniaturization of pattern rules. Logic devices, in particular, are driving this miniaturization. The most cutting-edge miniaturization technology is ArF immersion lithography, with double patterning, triple patterning, and quadruple patterning being used to mass-produce 10nm-node devices, and studies are also underway to develop 7nm-node devices using next-generation extreme ultraviolet (EUV) lithography with a wavelength of 13.5nm.

As miniaturization progresses, image blurring due to acid diffusion has become a problem (Non-Patent Document 1). It has been suggested that in order to ensure resolution in fine patterns with processing dimensions of 45 nm and below, it is important to control acid diffusion in addition to improving dissolution contrast, as has been proposed previously (Non-Patent Document 2). However, because chemically amplified resist compositions increase sensitivity and contrast through acid diffusion, attempts to minimize acid diffusion by lowering the post-exposure bake (PEB) temperature or shortening the PEB time result in significant decreases in sensitivity and contrast.

Suppressing acid diffusion by adding an acid generator that generates bulky acid is effective. Therefore, copolymerizing an onium salt acid generator with a polymerizable olefin into a polymer has been proposed. However, when forming patterns on resist films with feature sizes of 16 nm or smaller, it is believed that chemically amplified resist compositions cannot be used to form patterns due to acid diffusion, and the development of non-chemically amplified resist compositions is desired.

An example of a material for non-chemically amplified resist compositions is polymethyl methacrylate (PMMA). PMMA is a positive resist material whose main chain is scissed by EUV irradiation, reducing its molecular weight and improving its solubility in organic solvent developers.

Hydrogen silsesquioxane (HSQ) is a negative resist material that becomes insoluble in alkaline developers due to crosslinking caused by a condensation reaction of silanols generated by EUV irradiation. Chlorine-substituted calixarenes also function as negative resist materials. These negative resist materials have small molecular size before crosslinking and are free of blurring due to acid diffusion, resulting in low edge roughness and extremely high resolution, and are used as pattern transfer materials to indicate the resolution limit of exposure equipment. However, these materials have insufficient sensitivity and require further improvement.

One of the challenges in developing materials for EUV lithography is the low photon count in EUV exposure. EUV energy is much higher than that of ArF excimer laser light, and the photon count in EUV exposure is one-fourteenth that of ArF exposure. Furthermore, the dimensions of patterns formed with EUV exposure are less than half those of ArF exposure. This makes EUV exposure susceptible to variations in photon count. Variations in photon count in the extremely short-wavelength radiation region are a physical phenomenon known as shot noise, and their effects cannot be eliminated. For this reason, so-called stochastics has attracted attention. While the effects of shot noise cannot be eliminated, methods for reducing them are being discussed. Shot noise not only increases dimensional uniformity (CDU) and line-width roughness (LWR), but also has been observed to cause hole blockage with a probability of one in several million. When holes become blocked, electrical conductivity is poor and the transistor does not function, adversely affecting the performance of the entire device. When considering practical sensitivity, resist compositions based on PMMA or HSQ are significantly affected by stochastics and are unable to achieve the desired resolution performance.

As a method for reducing the effects of shot noise on the resist side, the introduction of elements that highly absorb EUV light has attracted attention. Patent Document 1 proposes a chemically amplified resist composition containing iodine atoms that highly absorb EUV light. However, as mentioned above, chemically amplified resist compositions cannot achieve excellent resolution performance in EUV lithography, where processing dimensions will become increasingly finer in the future.

Patent Document 2 proposes a negative resist composition that uses a tin compound. Because this composition contains tin, which has high absorption of EUV light, as its main component, it improves stochastics and achieves high sensitivity and high resolution. However, this type of metal resist has many issues, including insufficient solubility in resist solvents, storage stability, and defects caused by post-etching residue.

In response to this, Patent Document 3 proposes a positive resist composition that uses a hypervalent iodine compound. Because this composition contains iodine, which has high absorption of EUV light, it has improved stochastics, similar to metal resists, and can achieve high sensitivity and high resolution. Furthermore, because it is composed solely of organic molecules, it can address issues with metal resists, such as developer solubility and defects caused by residues. However, its performance as a resist material is still unsatisfactory, and there is a need for the development of resist materials that are useful for forming even finer patterns.

Japanese Patent Application Laid-Open No. 2018-5224 Special Publication No. 2021-503482 Japanese Patent Application Laid-Open No. 2023-167368

SPIE Vol. 5039 p1 (2003) SPIE Vol. 6520 p65203L-1 (2007)

The present invention has been made in consideration of the above circumstances, and aims to provide a resist composition that exhibits excellent sensitivity and resolution in photolithography using high-energy beams, particularly electron beam (EB) lithography and EUV lithography, as well as a pattern formation method using the resist composition.

As a result of extensive research into achieving the above-mentioned objectives, the inventors discovered that a resist composition primarily composed of a hypervalent iodine compound having a specific carboxylate ligand and a carboxy group-containing polymer produces a resist film that exhibits extremely high sensitivity and excellent resolution, and is extremely effective for precise microfabrication, leading to the creation of the present invention.

That is, the present invention provides the following resist composition and pattern forming method.
1. A resist composition comprising a hypervalent iodine compound represented by the following formula (1), a carboxy group-containing polymer, and a solvent:
(In the formula, m is 0 or 1. When m is 0, n is an integer of 0 to 4, and when m is 1, n is an integer of 0 to 6.
R ¹ is a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.
^R2 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 or greater, each ^R2 may be the same as or different from another R2. Furthermore, multiple ^R2s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.
R ³ is a carbonyl group or a hydrocarbylene group having 1 to 10 carbon atoms which may contain a heteroatom.
*1 and *2 represent bonds to carbon atoms of the aromatic ring in the formula. However, *1 and *2 are bonded to adjacent carbon atoms of the aromatic ring.)
2. The resist composition of 1, wherein the carboxy group-containing polymer contains a repeating unit represented by the following formula (2):
(In the formula, R ^A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group.
X ^A is a single bond, a phenylene group, a naphthylene group, or *-C(═O)-O-X ^A1 -. X ^A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom of the main chain.
3. The resist composition of 1 or 2, further comprising a hypervalent iodine compound represented by the following formula (3):
(wherein k is an integer from 0 to 5.
R ¹¹ and R ¹² are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. R ¹¹ and R ¹² may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms.
R ¹³ is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When k is 2, 3, 4, or 5, each R ¹³ may be the same as or different from another R 13. Furthermore, multiple R ^13s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.
4. A laminate comprising a substrate and a resist film formed on the substrate from a resist composition according to any one of 1 to 3.
5. The laminate of 4, further comprising a resist underlayer film between the substrate and the resist film.
6. A pattern forming method comprising the steps of: forming a resist film on a substrate, or on an underlayer film of a substrate laminated with an underlayer film, using the resist composition of any one of 1 to 3; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.
7. The pattern formation method according to 6, wherein the high-energy beam is an electron beam or extreme ultraviolet light.
8. The pattern forming method according to 6 or 7, wherein the developer dissolves exposed areas but does not dissolve unexposed areas.
9. The pattern forming method according to 6 or 7, wherein the developer dissolves the unexposed areas but does not dissolve the exposed areas.
10. A laminate comprising a substrate and a resist film on the substrate, wherein the resist film contains a polymer containing a repeating unit represented by the following formula (4):
(In the formula, m is 0 or 1. When m is 0, n is an integer of 0 to 4, and when m is 1, n is an integer of 0 to 6.
^R2 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 or greater, each ^R2 may be the same as or different from another R2. Furthermore, multiple ^R2s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.
R ³ is a carbonyl group or a hydrocarbylene group having 1 to 10 carbon atoms which may contain a heteroatom.
*1 and *2 represent bonds to carbon atoms of the aromatic ring in the formula, provided that *1 and *2 are bonded to adjacent carbon atoms of the aromatic ring.
R ^A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group.
X ^A is a single bond, a phenylene group, a naphthylene group, or *-C(═O)-O-X ^A1 -. X ^A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom of the main chain.
11. The laminate of 10, comprising a resist underlayer film between the substrate and the resist film.
12. A pattern forming method comprising the steps of exposing a resist film of the laminate of either 10 or 11 to high-energy rays, and developing the exposed resist film using a developer.
13. The pattern formation method according to 12, wherein the high-energy beam is an electron beam or extreme ultraviolet light.
14. The pattern forming method according to 12 or 13, wherein the developer dissolves exposed areas but does not dissolve unexposed areas.
15. The pattern forming method according to 12 or 13, wherein the developer dissolves the unexposed areas but does not dissolve the exposed areas.

The resist composition of the present invention combines high sensitivity and high resolution, making it extremely useful for forming fine patterns, particularly in EB lithography and EUV lithography.

[Resist Composition]
The resist composition of the present invention comprises a hypervalent iodine compound having a specific carboxylate ligand, a carboxy group-containing polymer, and a solvent.

[Hypervalent iodine compounds]
The hypervalent iodine compound is a three-coordinate hypervalent iodine compound represented by the following formula (1).

In formula (1), m is 0 or 1. When m is 0, n is an integer from 0 to 4, and when m is 1, n is an integer from 0 to 6. n is preferably 0, 1, 2, 3, or 4, more preferably 0, 1, 2, or 3, even more preferably 0, 1, or 2, and most preferably 0 or 1.

In formula (1), ^R1 is a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 10 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0 ^2,6 ]decanyl, and adamantyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl and allyl; aryl groups having 6 to 10 carbon atoms, such as phenyl and naphthyl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- groups in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), etc. ^R1 is preferably a hydrocarbyl group having 1 to 4 carbon atoms or a fluorinated hydrocarbyl group having 1 to 4 carbon atoms, more preferably a hydrocarbyl group having 1 to 4 carbon atoms.

In formula (1), ^R2 is a halogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 40 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0 ^2,6 ]decanyl, adamantyl, and adamantylmethyl; aryl groups having 6 to 40 carbon atoms, such as phenyl, naphthyl, and anthracenyl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, or some of the —CH ₂ — groups in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring or a carboxylic acid anhydride (—C(═O)—O—C(═O)—). When n is 2 or greater, each R ² may be the same or different. In addition, multiple R ^2s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.

In formula (1), ^R3 is a carbonyl group or a hydrocarbylene group having 1 to 10 carbon atoms which may contain a heteroatom. The hydrocarbylene group having 1 to 10 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-2,3-diyl group, butane-1,4-diyl group, 2-methylpropane-1,2-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, adamantanediyl group, and tricyclo[5.2.1.0 ^2,6 ] cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as a decanediyl group; alkenediyl groups having 2 to 10 carbon atoms, such as a vinylene group or a propenylene group; arylene groups having 6 to 10 carbon atoms, such as a phenylene group, a methylphenylene group, an ethylphenylene group, an n-propylphenylene group, an isopropylphenylene group, an n-butylphenylene group or a naphthylene group; and groups obtained by combining these. In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- groups of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbylene group containing a hydroxy group, a cyano group, a halogenated alkyl group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), etc. ^R3 is preferably a carbonyl group, a hydrocarbylene group having 1 to 4 carbon atoms or a fluorinated hydrocarbylene group having 1 to 4 carbon atoms.

In formula (1), *1 and *2 represent bonds to the carbon atoms of the aromatic ring in the formula. However, *1 and *2 are bonded to adjacent carbon atoms of the aromatic ring. The combinations of *1, *2, and m can have the following four patterns:
(wherein n, ^R2 and ^R3 are the same as above. The dashed line represents a bond to ^R1 -C(=O)-O-.)

Specific examples of the hypervalent iodine compound represented by formula (1) include, but are not limited to, the following: In the following formula, Me is a methyl group.

[Carboxy group-containing polymer]
The carboxyl group-containing polymer preferably contains a carboxyl group-containing repeating unit, which is preferably represented by the following formula (2):

In formula (2), R ^A represents a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. X ^A represents a single bond, a phenylene group, a naphthylene group, or *-C(═O)-O-X ^A1 -. X ^A1 represents a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

Specific examples of the carboxy group-containing repeating unit include, but are not limited to, the following: In the following formula, R ^A is the same as defined above.

The carboxy group-containing polymer may further contain repeating units other than the carboxy group-containing repeating units (hereinafter also referred to as "other repeating units"). The other repeating units are not particularly limited, but are preferably those that can improve the solubility in solvents of polymers that are poorly soluble in solvents with only carboxy group-containing repeating units. Such repeating units are preferably repeating units having a hydrocarbyl group having 1 to 20 carbon atoms and optionally containing at least one selected from a halogen atom, a hydroxy group, a cyano group, a carbonyl group, a nitro group, a sulfonic acid group, an amino group, an isocyanate group, an amide bond, an imide bond, an ester bond, an ether bond, a sulfide bond, a carbonate bond, a lactone ring, and a sultone ring.

Specific examples of the other repeating units include, but are not limited to, those shown below: In the following formula, R ^A is the same as defined above, and X ^B each independently represents —CH ₂ — or —O—.

In the carboxy group-containing polymer, the molar ratio of the carboxy group-containing repeating units to the other repeating units is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

The weight-average molecular weight (Mw) of the carboxyl group-containing polymer is preferably 1,000 to 500,000, and more preferably 3,000 to 100,000. In the present invention, Mw is a polystyrene-equivalent measurement value obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

Furthermore, if the carboxyl group-containing polymer has a broad molecular weight distribution (Mw/Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in foreign matter appearing on the pattern after exposure, or the pattern shape may be degraded. Therefore, as the effects of Mw and Mw/Mn tend to become greater as pattern rules become finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that the carboxyl group-containing polymer have a narrow Mw/Mn distribution of 1.0 to 2.0.

One example of a method for synthesizing the carboxyl group-containing polymer is to polymerize a monomer that provides the repeating unit described above in an organic solvent by adding a radical polymerization initiator and heating the resulting mixture.

Specific examples of organic solvents used in the polymerization reaction include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), and gamma-butyrolactone (GBL). Specific examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of the polymerization initiator added is preferably 0.01 to 25 mol% of the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, and more preferably 60 to 100°C. The reaction time is preferably 2 to 24 hours, and from the perspective of production efficiency, more preferably 2 to 12 hours.

The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel, or an initiator solution may be prepared separately from the monomer solution and then fed to the reaction vessel independently. Because radicals generated from the initiator during the waiting time may accelerate the polymerization reaction and produce ultra-high molecular weight polymers, it is preferable to prepare the monomer solution and initiator solution independently and add them dropwise from a quality control perspective. The acid labile groups introduced into the monomer may be used as is, or they may be protected or partially protected after polymerization. To adjust the molecular weight, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may also be used in combination. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

In the resist composition of the present invention, the hypervalent iodine compound and the carboxy group-containing polymer are preferably contained so that the molar ratio of the hypervalent iodine compound to the carboxylic acid-containing repeating units in the polymer is 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. The hypervalent iodine compound may be used alone, or two or more types may be used in combination. The carboxy group-containing polymer may be used alone, or two or more types with different composition ratios, Mw, and/or Mw/Mn may be used in combination.

[Other hypervalent iodine compounds]
The resist composition of the present invention may contain a hypervalent iodine compound represented by the following formula (3) (hereinafter also referred to as other hypervalent iodine compounds). By adding the other hypervalent iodine compounds, it is possible to control the reactivity to light and adjust the sensitivity.

In formula (3), k is an integer from 0 to 5.

In formula (3), R ¹¹ and R ¹² are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. R ¹¹ and R ¹² may also be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 10 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0 ^2,6 ]decanyl, and adamantyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl and allyl; aryl groups having 6 to 10 carbon atoms, such as phenyl and naphthyl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- groups in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), etc. ^R11 and ^R12 are preferably hydrocarbyl groups having 1 to 4 carbon atoms or fluorinated hydrocarbyl groups having 1 to 4 carbon atoms, and more preferably hydrocarbyl groups having 1 to 4 carbon atoms.

In formula (3), ^R13 is a halogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 40 carbon atoms may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0 ^2,6 ]decanyl, adamantyl, and adamantylmethyl; aryl groups having 6 to 40 carbon atoms, such as phenyl, naphthyl, and anthracenyl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- groups in the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, resulting in the hydrocarbyl group containing a hydroxy group, a cyano group, a halogen atom, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride (-C(=O)-O-C(=O)-), etc. When k is 2, 3, 4 or 5, ^R13 may be the same as or different from one another, and multiple ^R13 may be bonded to one another to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.

Other specific examples of hypervalent iodine compounds include, but are not limited to, the following:

When the resist composition of the present invention contains other hypervalent iodine compounds, the total content ratio of the hypervalent iodine compound represented by Formula (1) and the other hypervalent iodine compounds relative to the carboxylic acid-containing repeating units in the polymer is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. Furthermore, the other hypervalent iodine compounds are preferably contained in a molar ratio relative to the hypervalent iodine compound represented by Formula (1) of other hypervalent iodine compound:hypervalent iodine compound represented by Formula (1) = 1:99 to 99:1, more preferably 1:99 to 50:50. The other hypervalent iodine compounds may be used alone or in combination of two or more different types.

[solvent]
The resist composition of the present invention contains a solvent. The solvent is not particularly limited as long as it can dissolve the hypervalent iodine compound represented by formula (1), the carboxy group-containing polymer, other hypervalent iodine compounds, and other components described below and can form a film. Such a solvent is preferably an organic solvent, and specific examples thereof include ketones such as cyclohexanone, methyl-2-n-pentyl ketone, and methyl isoamyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, 4-methyl-2-pentanol, and methyl 2-hydroxyisobutyrate; propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether; Examples of the solvent include ethers such as propylene glycol dimethyl ether and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono tert-butyl ether acetate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as γ-butyrolactone; and mixed solvents thereof.

The content of the solvent in the resist composition of the present invention is preferably an amount that results in a solids concentration in the resist composition of 0.1 to 20% by mass, more preferably an amount that results in a solids concentration in the resist composition of 0.1 to 15% by mass, and even more preferably an amount that results in a solids concentration in the resist composition of 0.1 to 10% by mass. In this specification, the term "solids" refers collectively to all components of the resist composition other than the solvent. The solvents may be used alone, or two or more may be mixed together.

The resist composition of the present invention may further contain a surfactant. The surfactant is preferably a fluorine-based and/or silicone-based surfactant. Specific examples of such surfactants include those described in paragraph [0276] of U.S. Patent Application Publication No. 2008/0248425. Furthermore, surfactants other than the fluorine-based and/or silicone-based surfactants described in paragraph [0280] of U.S. Patent Application Publication No. 2008/0248425 can also be used.

When the resist composition of the present invention contains the surfactant, its content is preferably 0.0001 to 2% by mass of the total solids content. The surfactant may be used alone or in combination of two or more types.

The resist composition of the present invention may further contain at least one selected from a radical scavenger and a crosslinking agent. This makes it possible to control the photoreaction during photolithography and adjust the sensitivity.

Specific examples of the radical scavengers include hindered phenols, quinones, hindered amines, and thiol compounds. Specific examples of the hindered phenols include dibutylhydroxytoluene and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of the quinones include 4-methoxyphenol (methoquinone) and hydroquinone. Specific examples of the hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Specific examples of the thiols include dodecanethiol and hexadecanethiol.

When the resist composition of the present invention contains the radical scavenger, its content is preferably 0.01 to 10 mass% of the total solids content. The radical scavenger may be used alone or in combination of two or more types.

Specific examples of the crosslinking agent include compounds having a carbon-carbon unsaturated bond as a functional group, such as a vinyl group, a (meth)acrylate group, an allyl group, an alkynyl group, or an aromatic ring. Specific examples of compounds having a vinyl group include linear alkenes, branched alkenes, and cyclic alkenes, which may have a substituent. Specific examples of compounds having a (meth)acrylate group include acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, which may have a substituent. Specific examples of compounds having an allyl group include allyl alcohol, allyl ether, allyl ester, allyl amide, allyl amine, and allyl group-containing isocyanurates, which may have a substituent. Specific examples of compounds having an alkynyl group include linear alkynes, branched alkynes, cyclic alkynes, alkynyl alcohol, alkynyl ether, alkynyl ester, alkynyl amide, alkynyl amine, and alkynyl group-containing isocyanurates, which may have a substituent. Specific examples of compounds having an aromatic ring include arenes, heteroarenes, styrene, stilbene, phenylacetylene, acenaphthylene, chalcone, and the like, which may have a substituent. The crosslinking agent may have only one or more of the above functional groups. The number of functional groups contained in the crosslinking agent is preferably 1 to 10, and more preferably 2 to 8.

When the resist composition of the present invention contains the crosslinking agent, its content is preferably 0.01 to 50 mass% of the total solids content. The crosslinking agents may be used alone or in combination of two or more.

As mentioned above, the resist composition of the present invention contains a hypervalent iodine compound and a carboxy group-containing polymer as its main components, but does not contain an acid-labile group-containing base polymer or a photoacid generator, as are contained in conventional chemically amplified resist compositions. However, with the resist composition of the present invention, a difference in solubility occurs between the exposed and unexposed areas, particularly upon exposure to EB or EUV, making it possible to form positive or negative patterns. The mechanism behind this is not completely clear, but is presumed to be as follows, for example.

The hypervalent iodine compound represented by formula (1) is a tricoordinate compound with a carboxylate ligand. When such a tricoordinate iodine compound is mixed with a carboxylic acid compound, an exchange of the carboxylate ligand is thought to occur through an equilibrium reaction. If the original carboxylate ligand can be removed in some way, a hypervalent iodine compound with a new ligand is generated. For example, 1-acetoxy-1,2-benziodoxol-3-(1H)-one, a relatively readily available hypervalent iodine compound, is mixed with a high-molecular-weight carboxylic acid compound, and the resulting low-boiling acetic acid is removed to complete the ligand exchange. If the carboxylic acid compound is a polymer, the polymer and the hypervalent iodine compound combine to form a high-molecular-weight hypervalent iodine compound.

High-molecular-weight hypervalent iodine compounds are generated during film formation. This is because even if such high-molecular-weight hypervalent iodine compounds are synthesized in advance, they are insoluble in many organic solvents and therefore cannot be used to prepare a solution. This is presumably because hypervalent iodine compounds, which have low solvent solubility due to their inherent high polarization, become even less soluble when a high-molecular-weight carboxylic acid-containing polymer is used as a ligand. Therefore, it is desirable to complete the ligand exchange reaction and form a resist film by removing the original low-molecular-weight carboxylic acid component during film formation and the subsequent baking process.

The resist film formed in this manner is presumed to contain a polymer in which a carboxyl group-containing polymer and a hypervalent iodine compound are bonded together, that is, the polymer is presumed to contain a repeating unit represented by the following formula (4):
(wherein m, n, ^R2 , ^R3 , *1, *2, R ^A and ^XA are the same as defined above.)

The resist film of the present invention formed on the substrate in this manner undergoes a change in polarity when its main component, the hypervalent iodine compound, is decomposed by light, and a pattern is formed by the development process. By appropriately selecting the developer, either a positive or negative pattern can be formed.

Based on the above speculation, it can be said that the resist composition of the present invention is a non-chemically amplified resist composition. Unlike conventional chemically amplified resist compositions, the resist composition of the present invention does not require an acid-labile group-containing base polymer or a photoacid generator. Therefore, adverse effects due to acid diffusion (e.g., image blurring) do not occur, making it possible to resolve fine patterns.

The resist composition of the present invention is particularly effective in EUV lithography. This is because the resist composition of the present invention contains iodine atoms with high absorption capacity for EUV light, and the hypervalent iodine compound represented by formula (1) contains only one carboxylate ligand that can undergo the aforementioned ligand exchange. This prevents crosslinking between polymers during film formation, and allows polarity change to occur at a lower exposure dose than when other hypervalent iodine compounds are used alone. In other words, these features enable the resist composition of the present invention to achieve high sensitivity, high resolution, and low LWR.

Metal resists primarily composed of metal tin compounds, which, like iodine atoms, have a high absorption capacity for EUV light, have been reported as resist compositions for EUV lithography capable of forming fine patterns (see, for example, Patent Document 2). However, as mentioned above, such metal resists suffer from numerous problems, including insufficient solubility in solvents, poor storage stability, and defects due to post-etching residues caused by the presence of metal elements. In contrast, the resist composition of the present invention does not contain metal elements, making it more advantageous than metal resists in terms of defects and eliminating the issue of solvent solubility. Furthermore, the resist composition of the present invention can be used in both positive-tone and negative-tone resists, making it versatile. For example, in the contact hole formation process, metal resists developed using negative-tone development require a reversal process step after pillar pattern formation, whereas positive-tone resists do not require such a step. Therefore, from the perspective of process simplicity, the resist composition of the present invention is more useful than metal resists.

JP 2015-180928 A and JP 2018-095853 A describe resist compositions containing a hypervalent iodine compound as an additive and resist compositions incorporating a hypervalent iodine compound into the polymer backbone of a base polymer. However, these patent documents only describe the resist compositions' ability to improve line edge roughness, and make no mention of the possibility of hypervalent iodine compounds undergoing photodecomposition or functioning as materials for non-chemically amplified resist compositions. Furthermore, according to the descriptions of blending amounts and specific examples, hypervalent iodine compounds are not the main component. Furthermore, Patent Document 3 proposes a positive resist composition using a hypervalent iodine compound, but does not describe the hypervalent iodine compound represented by Formula (1) of the present invention, nor does it mention at all that using such a compound improves sensitivity or resolution. Therefore, it is believed that these patent documents do not suggest the non-chemically amplified resist composition of the present invention, which exhibits extremely high sensitivity, excellent resolution, and is extremely effective for precise microfabrication. In other words, it can be said that the present invention provides a clearly novel resist composition and pattern formation method.

[Pattern formation method]
When the resist composition of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be applied. For example, a pattern formation method can include a method comprising the steps of forming a resist film on a substrate using the resist composition, exposing the resist film to high-energy rays, and, if necessary, developing the exposed resist film using a developer.

First, the resist composition of the present invention is applied to a substrate for integrated circuit production, or to a substrate having a laminated underlayer film (e.g., Si, SiO ₂ , SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating), or to a substrate for mask circuit production, or to a substrate having a laminated underlayer film (e.g., Cr, CrO, CrON, MoSi ₂ , or SiO ₂ ), by a suitable coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or doctor coating, to a coating thickness of 0.01 to 2 μm. This is then prebaked on a hot plate, preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form a resist film. The underlayer film refers to a film formed between the substrate and the resist film in a multilayer resist process. The type of underlayer film is not particularly limited, and conventionally known underlayer films can be used.

The resist film is then exposed to high-energy radiation. Examples of such high-energy radiation include ultraviolet radiation, far ultraviolet radiation, EB, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation are used as the high-energy radiation, the exposure dose is preferably about 1 to 300 mJ/ ^cm² , more preferably about 10 to 200 mJ/ ^cm² , either directly or using a mask for forming the desired pattern. When EB is used as the high-energy radiation, the exposure dose is preferably about 0.1 to 2000 μC/ ^cm² , more preferably about 0.5 to 1500 μC/ ^cm² , either directly or using a mask for forming the desired pattern. The resist composition of the present invention is particularly suitable for fine patterning using EB or EUV, among other high-energy radiations.

After exposure, PEB is performed as needed. This is preferably performed on a hot plate or in an oven at 30 to 150°C for 10 seconds to 30 minutes, more preferably at 60 to 120°C for 30 seconds to 20 minutes.

After exposure or PEB, the film is developed with a developer as needed to achieve patterning. Developers used in this process include alkaline aqueous solutions such as tetramethylammonium hydroxide solution; 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, isopropyl alcohol, isoamyl alcohol, n-butanol, n-pentanol, cyclohexanol, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, cyclohexyl acetate, propyl formate, butyl formate, isobutyl formate, and formic acid. Examples of organic solvents that can be used include pentyl, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, 2-phenylethyl acetate, 2-propanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, and 4-methyl-2-pentanol. These developers may be used alone or in combination.

After development, rinse if necessary. A preferred rinse solution is a solvent that is miscible with the developer but does not dissolve the resist film. Examples of such solvents include alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents with 6 to 12 carbon atoms. Water may also be used as a rinse solution instead of an organic solvent.

Rinsing can reduce the occurrence of resist pattern collapse and defects. Rinsing is not always necessary, and eliminating rinsing can reduce the amount of solvent used.

The present invention will be specifically explained below using synthesis examples, working examples, and comparative examples, but the present invention is not limited to the following examples.

[1] Synthesis of hypervalent iodine compound [Synthesis Example 1-1] Synthesis of hypervalent iodine compound I-1

A solution of 13.6 g of starting compound SM-1 (iodobenzoic acid) in 40 g of acetonitrile was added dropwise to a solution of 40 g of Oxone (registered trademark) (potassium peroxymonosulfate) dissolved in 40 g of water at room temperature. After the dropwise addition, the mixture was stirred for 2 hours, and the precipitated solid was separated by filtration. The resulting solid was washed with 40 mL of water, then with 40 mL of acetone, and dried under reduced pressure at 40°C to obtain intermediate In-1 as a solid (yield: 11.6 g, 81%). Next, 8 g of In-1 and 27 mL of acetic anhydride were mixed and stirred at 140°C for 2 hours. The reaction solution was returned to room temperature, and the precipitated solid was separated by filtration. The resulting solid was washed with diisopropyl ether and dried under reduced pressure at 40°C to obtain the desired hypervalent iodine compound I-1 as a solid (yield: 7.0 g, 5%).
The results of measurement of the nuclear magnetic resonance spectrum ( ¹ H-NMR/DMSO-d ₆ ) and single quadrupole mass spectrometry of the hypervalent iodine compound I-1 are shown below.
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 2.25 (s, 3H), 7.75 (m, 1H), 7.78 (m, 1H), 8.05 (m, 2H) ppm.
Single quadrupole mass spectrometry (ESI): POSITIVE M ⁺ H ⁺ 307.0 (equivalent to C ₉ H ₇ IO ₄ )

[Synthesis Example 1-2] Synthesis of hypervalent iodine compound I-2

A hypervalent iodine compound I-2 was synthesized (yield 86%) in the same manner as in Synthesis Example 1-1, except that the starting compound SM-2 was used instead of the starting compound SM-1.
The results of measurement of the nuclear magnetic resonance spectrum ( ¹ H-NMR/DMSO-d ₆ ) and single quadrupole mass spectrometry of the hypervalent iodine compound I-2 are shown below.
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 2.21 (s, 3H), 7.61 (m, 1H), 7.72 (d, J=8.2Hz, 1H), 7.95 (d, J=4.2Hz, 1H) ppm.
Single quadrupole mass spectrometry (ESI): POSITIVE M ⁺ H ⁺ 325.0 (equivalent to C ₉ H ₆ FIO ₄ )

[Synthesis Example 1-3] Synthesis of hypervalent iodine compound I-3

To a solution of 15 g of the starting compound SM-3 dissolved in 40 g of acetonitrile, 3.4 g of trichloroisocyanuric acid was added. After stirring at room temperature for 30 minutes, the precipitated solid was filtered off to obtain intermediate In-3 (yield: 10.6 g, 65%).
Next, 8 g of IM-3, 3.3 g of silver acetate, and 100 g of acetonitrile were mixed and stirred at room temperature for 10 hours, and the precipitated solid was filtered off. The resulting solid was extracted with acetonitrile, and the extract was evaporated under reduced pressure to obtain the target hypervalent iodine compound I-3 as a solid (yield: 8.5 g, 100%).
The results of measurement of the nuclear magnetic resonance spectrum ( ¹ H-NMR/CDCl ₃ ) and single quadrupole mass spectrometry of the hypervalent iodine compound I-3 are shown below.
¹ H-NMR (500MHz, CDCl ₃ ) δ 2.18 (s, 3H), 7.61-7.79 (m, 3H), 7.93 (d, J=8.4Hz, 1H) ppm.
Single quadrupole mass spectrometry (ESI): POSITIVE M ⁺ H ⁺ 428.9 (equivalent to C ₁₁ H ₈ F ₆ IO ₃ )

[2] Polymer Synthesis The monomers used in the synthesis of the polymer are as follows:

Synthesis Example 2-1 Synthesis of Polymer P-1 Monomer a-1 (56 g), monomer b-1 (105 g), 5.4 g of V-601 (FUJIFILM Wako Pure Chemical Industries, Ltd.), and 180 g of MEK were placed in a flask under a nitrogen atmosphere to prepare a monomer-polymerization initiator solution. 55 g of MEK was placed in a separate flask under a nitrogen atmosphere and heated to 80°C with stirring, after which the monomer-polymerization initiator solution was added dropwise over 4 hours. After completion of the dropwise addition, stirring was continued for 2 hours while maintaining the temperature of the polymer solution at 80°C, and then the solution was cooled to room temperature. The resulting polymer solution was added dropwise to 4,000 g of vigorously stirred hexane, and the precipitated polymer was separated by filtration. The resulting polymer was further washed twice with 1,200 g of hexane and then vacuum-dried at 50°C for 20 hours to obtain polymer P-1 in the form of a white powder (yield: 155 g, 96%). Polymer P-1 had an Mw of 7700 and an Mw/Mn of 1.82. Note that Mw is a value measured in terms of polystyrene by GPC using THF as a solvent.

Synthesis Examples 2-2 to 2-10: Synthesis of Polymers P-2 to P-10 The polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of each monomer were changed.

[3] Preparation of resist composition [Examples 1-1 to 1-16, Comparative Examples 1-1 to 1-3]
Resist compositions (R-01 to R-16) and a comparative resist composition (CR-01) were prepared by dissolving a hypervalent iodine compound, another hypervalent iodine compound, and a polymer in a solvent containing 0.01 mass% of a surfactant (PF-636, Omnova) according to the compositions shown in Table 2 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter. Comparative resist compositions (CR-02 to CR-03) were prepared by dissolving a polymer, a photoacid generator, and a sensitivity adjuster in a solvent containing 0.01 mass% of a surfactant (PF-636, Omnova) according to the compositions shown in Table 3 below, and filtering the resulting solution through a 0.2 μm Teflon (registered trademark) filter.

In Tables 2 and 3, the other hypervalent iodine compound O-1, photoacid generator PAG-1, sensitivity adjuster Q-1, and solvent are as follows:

Solvent: PGMEA (propylene glycol monomethyl ether acetate)
AcOH (acetic acid)
HBM (2-hydroxyisobutyric acid methyl ester)
PA (propionic acid)
GBL (γ-butyrolactone)

[4] EUV lithography evaluation (line and space pattern, positive tone development)
[Examples 2-1 to 2-16, Comparative Examples 2-1 to 2-3]
Each resist composition (R-01 to R-16, CR-01 to CR-03) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% by mass of silicon) manufactured by Shin-Etsu Chemical Co., Ltd., and pre-baked (PAB) for 60 seconds at the temperature listed in Table 4 using a hot plate to produce a 40 nm thick resist film. A 36 nm line and space (LS) 1:1 pattern was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), and then PEB was performed on a hot plate at the temperature listed in Table 4 for 60 seconds, followed by development for 30 seconds with the developer listed in Table 4 to form an LS pattern with a space width of 18 nm and a pitch of 36 nm.

The resulting resist patterns were evaluated as follows. The results are shown in Table 4.

[Sensitivity evaluation]
The LS pattern was observed using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ/cm ² ) for obtaining an LS pattern with a space width of 18 nm and a pitch of 36 nm was determined and taken as the sensitivity.

[LWR evaluation]
The LS pattern obtained by irradiation with the optimum exposure dose was measured at 10 points in the longitudinal direction of the space width using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the space width pattern obtained.

[Limiting resolution evaluation]
The limiting line width (nm) that can be resolved when forming a pattern by gradually increasing the exposure dose from the optimum exposure dose at which the LS pattern is formed was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a finer pattern can be formed.

Developer: nBA (butyl acetate)
CHA (cyclohexyl acetate)
TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[5] EUV lithography evaluation (line and space pattern, negative tone development)
[Examples 3-1 to 3-16, Comparative Examples 3-1 to 3-3]
Each resist composition (R-1 to R-16, CR-01 to CR-03) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% by mass of silicon) manufactured by Shin-Etsu Chemical Co., Ltd., and pre-baked (PAB) for 60 seconds at the temperature listed in Table 5 using a hot plate to produce a 40 nm thick resist film. A 36 nm line and space (LS) 1:1 pattern was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9, 90-degree dipole illumination), followed by baking (PEB) for 60 seconds on a hot plate at the temperature listed in Table 5, and then developed for 30 seconds using the developer listed in Table 5 to form an LS pattern with a space width of 18 nm and a pitch of 36 nm.

The resulting resist patterns were evaluated as follows. The results are shown in Table 4.

[Sensitivity evaluation]
The LS pattern was observed using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Tech Corporation, and the optimum exposure dose Eop (mJ/cm ² ) for obtaining an LS pattern with a space width of 18 nm and a pitch of 36 nm was determined and taken as the sensitivity.

[LWR evaluation]
The LS pattern obtained by irradiation with the optimum exposure dose was measured at 10 points in the longitudinal direction of the space width using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the space width pattern obtained.

[Limiting resolution evaluation]
The limiting line width (nm) that can be resolved when forming a pattern by gradually increasing the exposure dose from the optimum exposure dose at which the LS pattern is formed was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a finer pattern can be formed.

The results shown in Tables 4 and 5 demonstrate that the resist composition of the present invention exhibits excellent sensitivity, LWR, and resolution in both positive-tone and negative-tone development when forming line and space patterns using EUV exposure.

[6] EUV lithography evaluation (contact hole pattern)
[Examples 4-1 to 4-16, Comparative Examples 4-1 to 4-3]
Each resist composition (R-01 to R-16, CR-01 to CR-03) was spin-coated onto a Si substrate with a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd., and pre-baked (PAB) for 60 seconds at the temperature listed in Table 6 using a hot plate to produce a 50 nm thick resist film. The resist film was then exposed to light using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9/0.6, quadruple pole illumination, wafer dimensions with a 64 nm pitch and a +20% bias hole pattern mask), baked (PEB) for 60 seconds on a hot plate at the temperature listed in Table 6, and developed for 30 seconds using the developer listed in Table 6 to obtain a 32 nm hole pattern.

The resulting resist patterns were evaluated as follows, and the results are shown in Table 6.
[Sensitivity evaluation]
The contact hole pattern was observed using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and the optimum exposure dose Eop (mJ/cm ² ) for obtaining a hole pattern with a dimension of 32 nm was determined.

[CD Uniformity (CDU) Evaluation]
The dimensions of 50 hole patterns obtained by irradiation with the optimum exposure dose were measured, and the CDU was calculated as three times the standard deviation (σ). The smaller this value, the more uniform the hole diameter pattern.

[Limiting resolution evaluation]
The limiting hole diameter (nm) that can be resolved when forming a hole pattern by gradually decreasing the exposure dose from the optimum exposure dose at which the hole pattern is formed was determined using a critical dimension SEM (CG-6300) manufactured by Hitachi High-Technologies Corporation, and this was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, indicating that a pattern with a finer hole diameter can be formed.

The results shown in Table 6 demonstrate that the resist composition of the present invention exhibits excellent sensitivity, CDU, and resolution when forming contact hole patterns using EUV exposure.

Claims (15)

A resist composition comprising a hypervalent iodine compound represented by the following formula (1), a carboxy group-containing polymer, and a solvent:
(In the formula, m is 0 or 1. When m is 0, n is an integer of 0 to 4, and when m is 1, n is an integer of 0 to 6.
R ¹ is a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom.
^R2 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 or greater, each ^R2 may be the same as or different from another R2. Furthermore, multiple ^R2s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.
R ³ is a carbonyl group or a hydrocarbylene group having 1 to 10 carbon atoms which may contain a heteroatom.
*1 and *2 represent bonds to carbon atoms of the aromatic ring in the formula. However, *1 and *2 are bonded to adjacent carbon atoms of the aromatic ring.) 2. The resist composition according to claim 1, wherein the carboxyl group-containing polymer contains a repeating unit represented by the following formula (2):
(In the formula, R ^A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group.
X ^A is a single bond, a phenylene group, a naphthylene group, or *-C(═O)-O-X ^A1 -. X ^A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom of the main chain. 2. The resist composition according to claim 1, further comprising a hypervalent iodine compound represented by the following formula (3):
(wherein k is an integer from 0 to 5.
R ¹¹ and R ¹² are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. R ¹¹ and R ¹² may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms.
R ¹³ is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When k is 2, 3, 4, or 5, each R ¹³ may be the same as or different from another R 13. Furthermore, multiple R ^13s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded. A laminate comprising a substrate and a resist film formed on the substrate from the resist composition according to any one of claims 1 to 3. The laminate according to claim 4, further comprising a resist underlayer film between the substrate and the resist film. A pattern formation method comprising the steps of: forming a resist film on a substrate, or on an underlayer film of a substrate laminated with an underlayer film, using the resist composition according to any one of claims 1 to 3; exposing the resist film to high-energy radiation; and developing the exposed resist film using a developer. The pattern formation method according to claim 6, wherein the high-energy beam is an electron beam or extreme ultraviolet radiation. The pattern formation method according to claim 6, wherein the developer dissolves exposed areas but not unexposed areas. The pattern formation method according to claim 6, wherein the developer dissolves unexposed areas but does not dissolve exposed areas. A laminate comprising a substrate and a resist film on the substrate, wherein the resist film contains a polymer containing a repeating unit represented by the following formula (4):
(In the formula, m is 0 or 1. When m is 0, n is an integer of 0 to 4, and when m is 1, n is an integer of 0 to 6.
^R2 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 or greater, each ^R2 may be the same as or different from another R2. Furthermore, multiple ^R2s may be bonded to each other to form a ring together with the carbon atoms of the aromatic ring to which they are bonded.
R ³ is a carbonyl group or a hydrocarbylene group having 1 to 10 carbon atoms which may contain a heteroatom.
*1 and *2 represent bonds to carbon atoms of the aromatic ring in the formula, provided that *1 and *2 are bonded to adjacent carbon atoms of the aromatic ring.
R ^A is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group.
X ^A is a single bond, a phenylene group, a naphthylene group, or *-C(═O)-O-X ^A1 -. X ^A1 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom of the main chain. The laminate according to claim 10, further comprising a resist underlayer film between the substrate and the resist film. A pattern formation method comprising the steps of exposing a resist film of the laminate according to claim 10 or 11 to high-energy radiation and developing the exposed resist film using a developer. The pattern formation method according to claim 12, wherein the high-energy beam is an electron beam or extreme ultraviolet radiation. The pattern formation method according to claim 12, wherein the developer dissolves exposed areas but not unexposed areas. The pattern formation method according to claim 12, wherein the developer dissolves unexposed areas but not exposed areas.